Joint structure for concrete materials and the like

ABSTRACT

The invention is concerned with a joint structure adapted to be embedded in a concrete mass to accommodate relative displacements of sections thereof bounded in common by the joint. The joint structure includes an elongated, generally T-shaped channel having a horizontal flange and a web extending downwardly therefrom. The channel is adapted to be disposed within a concrete mass with the flange oriented in generally planar relation with the upper surface of the mass. The web is divided along a generally vertical plane disposed at its center into side-by-side components that are displaceable transversely relative to each other, and such components are equipped with anchors that effectively secure the same to the sections of the concrete mass bounded in common by the joint. At the time of insertion of the joint structure into a wet or uncured mass of concrete, a cap is removably secured to the channel in overlying relation with the flange thereof, and a protective strip of tape is located intermediate the flange and cap in attachment to the upper surface of the flange. After the wet concrete has been processed and finished, the cap and tape strip are removed to leave the channel in position within the concrete after it cures to serve as a contraction joint.

United States Patent 1 Stegmeier 1 Mar. 18, 1975 1 JOINT STRUCTURE FORCONCRETE MATERIALS AND THE LIKE [76] Inventor: William James Stegmeier,1021 C Shary Cir., Concord, Calif. 94520 [22] Filed: Oct. 30, 1973 [21]Appl. No.: 411,067

[52] US. Cl. 404/48, 52/396 [51] Int. Cl. E0lc 11/02 [58] Field ofSearch 404/68, 67, 66, 48, 47, 404/65, 69; 52/468, 396

[56] References Cited UNITED STATES PATENTS 1,397,678 11/1921 De Paoli404/47 X 2,834,198 5/1958 Goodman 404/65 X 2,937,065 5/1960 l-larza404/65 X 3,192,577 7/1965 Barr 52/396 X 3,276,335 10/1966Middlestadt.... 404/48 3.352.217 11/1967 Peters 404/65 3,413,900 12/1968Crone 404/48 3,434,401 3/1969 Kiewit 404/65 3,575,094 4/1971 Hewitt404/65 3,605,357 9/1971 Stegmeier 52/396 X Primary E.t'aminerNile C.Byers, Jr. Allurney, Agent, or FirmC. Michael Zimmerman, Esq.

[57] ABSTRACT The invention is concerned with a joint structure adaptedto be embedded in a concrete mass to accommodate relative displacementsof sections thereof bounded in common by the joint. The joint structureincludes an elongated, generally T-shaped channel having a horizontalflange and a web extending downwardly therefrom. The channel is adaptedto be disposed within a concrete mass with the flange oriented ingenerally planar relation with the upper surface of the mass. The web isdivided along a generally vertical plane disposed at its center intoside-by-side components that are displaceable transversely relative toeach other, and such components are equipped with anchors thateffectively secure the same to the sections of the concrete mass boundedin common by the joint. At the time of insertion of the joint structureinto a wet or uncured mass of concrete, a cap is removably secured tothe channel in overlying relation with the flange thereof, and aprotective strip of tape is located intermediate the flange and cap inattach ment to the upper surface of the flange. After the wet concretehas been processed and finished, the cap and tape strip are removed toleave the channel in position within the concrete after it cures toserve as a contraction joint.

24 Claims, 7 Drawing Figures PATENIEDHAR 1 19m saamapfz FIG.6

JOINT STRUCTURE FOR CONCRETE MATERIALS AND THE LIKE This inventionrelates to concrete slabs and the like and, more particularly, to jointstructures for use with concrete and similar materials to accommodaterelative displacements of sections thereof bounded in common by a jointembedded within a mass of such material.

Substantially all materials are subject to thermally induced expansionsand contractions, and construction materials such as concrete and thelike are specific examples thereof. The difficulties encountered bythermally-induced movements of such materials are aggravated when theyare used to surface relatively large ground areas, especially whenplaced directly upon an earthen bed, because of movement enforced on thematerials by changes in the earthen mass (sometimes referred to asheaving) as a consequence of moisture penetration, freezing, temblors,etc. All such movements enforced on these materials tend to crack thesame particularly when they are placed in tension because tensileweakness is a characteristic thereof especially with a nonhomogenousaggregate such as concrete.

Concrete, it may be noted, often tends to have cracks introduced thereinas a characteristic of its curing process. That is to say, the curing ofconcrete is a complex process entailing both a mechanical step ofmoisture evaporation and a chemical reaction in which heat is generatedas a by-product. The heat thus permeating the concrete mass can befairly substantial, and as the mass cools toward and upon termination ofthe chemical reaction, the consequent shrinkage or contraction of theconcrete mass tends to create fissures therein because of the tensilestresses that such movement of the concrete mass creates.

For all of these reasons, it is common to use joint structures withconcrete and similar materials at fixed intervals therealong to separatethe mass into sections which may move relative to each other along thecommon boundaries defined by the joint structures. In many instances,the joint structures employed are entirely utilitarian such as in theconstruction of roadways, and they may constitute a soft material suchas felt or fiber packing covered with tar for waterproofing purposes. Inother instances, the joint structures are employed for decorative oraesthetic purposes in addition to their utilitarian use, and examplesthereof are the decks of swimming pools (both domestic and commercial),domestic driveways and patios, and commercial malls. Decorative jointstructures of this type are often formed of plastic materials such aspolyvinylchloride, and many of those used heretofore have provided largeopen spaces within the interiors thereof and a thin exposed topwall thatlies substantially flush with the upper surfaces of the sections ofmaterial bounded in common thereby.

Respecting use of such joint structures with concrete, they are usuallypressed into the concrete after it has been poured and spread but beforeit has cured, and they do not extend completely through the concretemass because they are substantially shorter in depth that the concreternass into which they are embedded. The concrete mass is then tamped;surfaced with a large or bull float; troweled, grooved, and edged; andthen provided with a surface finish (a broomed or roughened surface) allafter the joint structures are in place. Although the typical decorativejoint structure of the type being considered does not penetrate from topto bottom of the concrete mass in which it is embedded, its presencetherein introduces a line of weakness along which the concrete mass maycrack or tissure, but the crack is covered by the joint structure whichconceals the same and accommodates relative displacements of thesections bounded in common thereby along the fissure.

Decorative joint structures now in common use have a number ofdisadvantages among which include the difficulty encountered by workmenusing the same in maintaining a straight-line disposition of the jointstructure while embedding the same in a concrete mass. The reason forthis difficulty is attributable to the flexibility of the jointstructures in lateral or transverse directions which permits thestructures to bend or snake as they are being pressed into the concrete.Another disadvantage is that the exposed topwalls of such structures arerelatively weak and are damaged (usually perforated) when a sharp objectis pressed thereagainst such as a pebble, narrow shoe heel, or childstoy. The reason that such joint structures are damaged along theirtopwall is that the latter is necessarily made relatively thin foreconomic purposes so that the entire quantity of material used in thejoint structure will not make the cost thereof so great that it ispracticably infeasible to use the same in a cost-conscious market.Another disadvantage with certain decorative joint structures is thatthey do not provide a positive water stop inhibiting the downward flowof water from the top surface of the concrete mass to the underlyingearthen bed via a path along the joint structure and any crackunderlying the same. Damage to a joint structure may increase thewater-leakage tendency which is undesirable because moisture penetratingthe underlying soil may cause the same to swell and heave especiallywith certain claytype soils present in many parts of California andelsewhere. It may also be observed that these joint structures arefrequently scuffed or marred and otherwise damaged during processing ofthe concrete masses after the joints are embedded therein, even thoughit is common to attempt to protect the joint structures with a layer oftape along the upper surface thereof. The use of such tape has itselfcreated problems because of the requirement that a durable, high-tackadhesive be employed in order to maintain the tape in protectiverelation with the joint structure, and adhesives of this type tend to beaffected by the sun and following exposure thereto may be exceedinglydifficult to remove, thereby resulting in an unsightly surface. Certainjoint structures are also .quite buoyant and tend to float out ofposition in the dense concrete prior to curing thereof.

In view of all of the foregoing, a general object of the presentinvention is to provide an improved joint structure adapted to beembedded in concrete materials and the like to accommodate relativedisplacements of sections thereof bounded in common by such joint, andwhich joint structure overcomes the various disadvantages andlimitations of conventional joint structures as noted hereinbefore.

Further objects, among others, of the present invention are in theprovision of an improved joint structure of the character described thatis relatively stiff or rigid especially in a transverse sense so that itcan be pressed into a wet concrete mass along a substantially straightline without difficulty by a workman, thereby obviating the time andexpense otherwise necessitated by conventional structures which in manyinstances requires the joint structure to be pre-set on supportsprovided for this purpose before the concrete is poured; that has arelatively thick and sturdy topwall or transverse flange directlyreinforced by underlying concrete which is thereby effective to resistperforation and analagous-type damage that characterizes the exposedtopwall of conventional joint structures; that serves as a water stop toprevent penetration therealong through an associated concrete mass ofwater collecting along the exposed upper surface ofa concrete mass andtending to flow downwardly therethrough along the juncture of theconcrete mass with the joint structure; that provides anchorage betweenthe joint structure and associated concrete sections bounded in commonthereby at locations sufficiently remote from the upper surfaces of theconcrete sections that cracks or fissures do not tend to be createdalong the exposed concrete surfaces because of the anchorage between thesections and joint structure; that pre-coves the concrete mass extendingalong the transverse flange of the joint structure to improve theaesthetic appearance of the upper surface of the cured concrete and tofacilitate manual coving of the lines of juncture of the flange with theconcrete mass; that incorporates protective features that enable workmento tamp, bull-float, trowel, and otherwise process a concrete massassociated with the joint structure without in any way damaging ordisfiguring the latter which then appears completely clean andunblemished at the time that the concrete has completely cured and isready for use; and that is nonbuoyant.

Additional objects and advantages of the invention, particularly asrespects specific features and characteristics thereof will becomeapparent as the specification continues.

In briefsummary form, the joint structure embodying the presentinvention in the particular form thereof disclosed herein may be takenfor convenience to be a tripartite structure including a generallyT-shaped channel, a cap removably secured thereto, and a strip ofprotective material disposed intermediate the cap and channel to protectthe upwardly facing surface of the latter. The T-shaped channel has atransverse flange defining a topwall adapted to be disposed in generallyplanar relation with the surfaces of a mass of concrete materialsubdivided into sections bounded in common by the joint structure. Thechannel further includes a web that extends downwardly from the flangeat substantially the midportion thereof, and the web is dividedintermediate its transverse edges into web components which, in theirinitial condition, are disposed in substantially parallel side-by-sidejuxtaposition. The web components are displaceable transversely relativeto each other, and they are each equipped with a transversely projectinganchor effective to secure the web component to an associated concretesection for movement therewith. One of the web components is longer thanthe other and is provided with an offset shoulder underlying the shorterweb to protect the same during insertion of the joint structure into amass of wet and uncured concrete.

An elongated cap that is substantially wider than the transverse flangeof the channel is equipped with downwardly extending spring fastenersthat extend generally along the length thereof and are adapted to gripthe edges of the flange to removably secure the cap thereto. The springfasteners have an arcuate configuration that tends to enforce a roundedrecess or covetype channel in the concrete mass along the transverseedges of the channel flange. A strip of protective material that maytake the form of a low-tack, pressuresensitive tape is interposedbetween the cap and upper surface of the transverse flange to protectsuch surface against damage since it will be the visible surface of thejoint structure after the concrete has cured. The tripartite jointstructure is pressed into an uncured mass of concrete at the properlocation, and after the initial processing of the concrete mass has beencompleted, the protective cap is removed. After the surface of theconcrete has been broomed or otherwise'finished, the protective tapestrip is removed to expose the unblemished upper surface of the jointstructure.

An embodiment of the invention is illustrated in the accompanyingdrawings, in which;

FIG. 1 is a broken perspective view illustrating a swimming pool havinga poured concrete deck thereabout equipped with joint structuresembodying the present invention; 1

FIG. 2 is a greatly enlarged, broken sectional perspective view ofaportion of such deck adjacent one of the joint structures, the viewbeing taken generally along the line 22 of FIG. 1;

FIG. 3 is a broken perspective view of the joint structure illustratingthe protective cap in spaced relation with the T-shaped channel and tapestrip thereon;

FIG. 4 is a broken, vertical sectional view illustrating the entirejoint structure embedded in a concrete mass after the upper surface ofsuch mass has been finished with a bull float and troweled;

FIG. 5 is a broken, vertical sectional view similar to that of FIG. 4,illustrating the interrelationship of such concrete mass and the jointstructure after the protective cap has been removed from the latter;

FIG. 6 is a broken, vertical sectional view similar to those of FIGS. 4and 5, illustrating the concrete mass and joint structure after an edgerhas been run along the joint structure to finish the coving, and afterwhich the protective tape has been removed from the exposed uppersurface of the joint structure; and

FIG. 7 is a broken, vertical sectional view similar to that of FIG. 6,but illustrating relative transverse displacement between the concretesections bounded in common by the joint structure, such relativedisplacement of the concrete sections being, for example, enforcedthereon by thermal contractions thereof.

The typifying use of joint structures is illustrated in FIG. 1, and itis perhaps one of the more difficult environments therefor in the sensethat substantial quantities of water are present, the earthen materialssupportingthe concrete may be fill and therefore subject to shifting,and thermally-induced expansions and contractions and differentialdisplacements may be aggravated over other uses for joint structures. Inmore specific terms, the environment depicted in FIG. 1 is a swimmingpool 10 having a poured concrete, cantilever deck 11 extendingthereabout. As respects the present invention, the pool 10 and deck 11may be substantially conventional, and each may be fabricated by anyconventional technique. It will be appreciated that the deck 11 issubjected to the presence of considerable quantities of water, and italso is exposed to substantial sunlight, thereby enforcing substantialthermallyinduced expansions and contractions thereon whereas thoseportions of the pool which are protected by the large body of watertherein, tend to remain at relatively constant temperature which mayresult in differential expansions and contractions as between the deck11 and those protected portions of the pool 10. The deck 11 and mass ofconcrete material defining the same is divided into sections by aplurality of joint structures 12 embedded therein. All of the jointstructures 12 may be identical, for this reason, only one such structurewill be described in detail hereinafter. It may be noted that each jointstructure 12 has a downwardly turned end 13 along the overhanging edgeportion of the cantilever deck 11 which may be provided in a variety ofmanners, such as by cutting out portions of the web of a straight jointstructure to bend or curve the same downwardly in general conformitywith the configuration of the overhanging edge ofthe deck.

As previously indicated, it is conventional to form pool decks ll ofpoured concrete, and the joint structure 12 is especially suited for usewith concrete masses especially because they tend to contract as theycure owing to the loss of heat developed during the chemical changesthat occur as a part of the curing process. Nevertheless, thejointstructures 12 can be used with other materials both for their decorativeeffect and for the functional'advantages attributable thereto. It willalso be understood that the joint structures may be employed in a greatnumber of environments where concrete and other materials are usedespecially when employed for surfacing purposes. Accordingly, the deck11 and use of the joint structures 12 in association therewith may betaken to be exemplary.

The joint structures illustrated in the drawings are of tripartiteconstruction, as shown most clearly in FIGS. 3 and 4. In this respect,each joint structure 12 includes a longitudinally extending, generallyT-shaped channel 14 having a transverse flange 15 disposed at its upperend and defining a topwall adapted to be disposed in generally planarrelation with the surfaces of concrete sections bounded in common by thejoint structure as shown in FIGS. 1, 2, and 4 through 7. The channel 14is an elongated continuous component and in the form shown, it isfabricated from a plastic material such as polyvinylchloride, and may bean extruded member cut into any appropriate length, ten feet forexample. Extending downwardly from the flange 15 at substantially thecenter thereof is a web 16 that is formed integrally with the flange.

As is seen most clearly in FIG. 7, the web 16 is divided intermediatethe transverse edges thereof, and at substantially its medial plane,into web components 17 and 18 that initially are disposed inside-by-side, substantially parallel juxtaposition but are displaceabletransversely relative to each other, as is evident by comparing FIGS. 6and 7. The web components 17 and 18 merge with each other and with theflange 15 so as to be integral therewith, and the juncture of thecomponents l7 and 18 adjacent the flange 15 defines a pivotal axis aboutwhich the web components are displaceable relative to each other. Theflange l5 and web 16 are substantially coextensive in length, and theweb is generally disposed with respect to the plane of the flange 15 atat 90 angle therewith. It will be apparent that the material from whichthe channel 14 is fabricated should be sufficiently flexible to enablethe web components 17 and 18 to be displaced repetitively relative toeach other in transverse directions in accordance with any relativedisplacements enforced thereon by the sections of the concrete massbounded in common by the joint structure.

Each of the web components 17 and 18 is equipped with a transverselyprojecting anchor effective to secure the same to the associatedconcrete section for movement therewith. In this reference, thecomponent 18 is provided with an anchor 19 disposed at generally rightangles with respect to the vertical plane of the web, and the web 18 issimilarly provided with an anchor 20 extending transversely therefrom.The anchors 19 and 20 are located at the lower terminus of the webcomponent 17,, and they are oriented in transverse alignment so thattogether they have a generally shaped configuration. Thus, the anchor 19has a generally horizontal web 21 substantially parallel in dispositionwith the flange l5 and terminating at its outer end in a verticallyextending flange 22 substantially paralleling the web 16. Similarly, theanchor 20 has a horizontally disposed flange 24 terminating in avertically oriented flange 25. It will be apparent that the anchors l9and 20 are located at the lower terminus of the web component 17 so thateach of the anchors is remote from the upper surface of the concretemass 11 in which the anchor structure is embedded. This relationship hasthe advantage of providing a substantial thickness of undisturbedconcrete intermediate each anchor and the upper surface of the concretemass so as to minimize any tendency for the concrete to crack or fissurebecause of the presence of the joint structure 12 and anchors 19 and 20thereof.

The web component 18 is seen to be longer than the web component 17, andit is provided adjacent the lower end of the web 17 with an offsetshoulder re cessed or grooved at 26 that underlies the web 17 andprotects the same during insertion of the joint structure into a mass ofuncured concrete, thereby tending to prevent the web component 17 fromspreading and to prevent solids such as stones and pebbles comprised bythe concrete mass from wedging beneath the web component 17. The webcomponent 17 has a rib or tongue 26 that seats within the groove 26 tofurther inhibit spreading of the webs. The web component 18 tapersdownwardly from the shoulder 26 thereof to a relatively sharp point oredge 27 that facilitates penetration of the concrete mass by the jointstructure.

The tripartite joint structure 12 further includes a cap 28 removablysecured to the channel 14 in generally overlying relation with theflange 15 thereof, as is evident in FIG. 4. in more particular terms,the cap 28 is in the form of a relatively flat or planar topwall 29 thatis substantially wider in transverse dimension than the flange 15 of thechannel 14, and it may be thinner than the flange 15, as illustrated inFIG. 4. The substantial transverse width of the topwall 29 providesconsiderable resistance to transverse bending of the cap particularlywhen it is united with the channel 14 so as to maintain the latter in astraightline disposition during insertion of the joint structure into aconcrete mass. The cap 28 further includes a pair of transversely spacedfasteners 30'and 31 in the nature of spring fingers or clips adapted toreleasably engage the flange 15 to removably secure the cap 28 thereto.The spring fasteners 30 and 31 are formed integrally with the topwall29, and they are substantially coterminus in length therewith. Not onlydo the fasteners 30 and 31 releasably secure the cap 28 to the channel14, but they also tend to stiffen the cap to constrain the same againsttransverse snaking especially when the cap is secured to the channel,and they are further configurated so as to impose a convex curvatureonto the concrete mass so as to define a cove finish along the jointstructure 12 after the concrete has cured, as is evident in FIGS. 2, 6,and 7. The protective cap 28 may be formed from a variety of materials,and in the embodiment illustrated, it is fabricated from a plastic suchas polystyrene which is less expensive than polyvinylchloride andtherefore preferred especially since it will be removed and discarded,if desired, after the joint structure is in position and the concretemass finished. The relatively thin dimension of the cap 28 may enablethe same to be coiled into a roll for storage and reuse, should this bedesired, and enables the same to be packaged conveniently for separatesale in the event that a customer should not wish to purchase the jointstructure with the channel 14 and cap 28 united, as in the conditionthereof shown in FIG. 4.

The tripartite joint structure 12 in the embodiment thereof illustrated,includes a strip of material 32 located intermediate the flange 15 andcap 28 to protect the upwardly-facing surface of the flange 15 duringcertain processing of the concrete mass with which the joint structureis used. The protective strip 32 is in the form of an elongated strip oftape which may have a paper backing equipped along one side thereof witha pressure-sensitive tape enabling the protective strip to be removablysecured to the flange 15. In the joint structure 12, a low-tack,pressure-sensitivetape may be employed which is not significantlyinfluenced by heat and light so as to become undesirably anchored to thesurface of the flange 15 because the protective strip is covered by thecap 28 during a substantial part of the manipulations performed on thewet concrete in finishing the same whereas in the absence of the cap 28,a high-tack, pressure-sensitive tape is necessarily employed to providesufficient adherence to the flange 15 to protect the same, but suchtapes are influenced by heat and light and become virtually impossibleto remove in many instances. Several tapes are available which can beused in the joint structure 12, and a specific example thereof, is alow-tack, pressure-sensitive Mylar tape of the type now in extensive useto protect transparent plastic material such as Plexiglass againstsurface scratching and marring during shipment and storage thereof.

In use of the joint structure 12, it can be preset on supports providedtherefor and the concrete mass thereafter poured, but there is nonecessity of doing so with the present joint structure since thestraightness thereof can be maintained during insertion into a mass ofwet or uncured concrete. Further, presetting a joint structure is asubstantial inconvenience as well as being time consuming because itinterferes with free movement of wheelbarrows used to distribute wetconcrete throughout the area to be covered thereby. Usually then, theconcrete mass is poured against forms provided for this purpose and isscreeded or leveled usually by moving a long two by four or similarpiece of lumber along the concrete mass while the two by four issupported on the upper edges of the form members. After this has beenaccomplished, the joint structure 12 in the configuration thereofillustrated in FIG. 4 is pushed downwardly into the concrete mass atsuitable locations the spacings between which are calculated inaccordance with the thickness of the concrete, composition thereof, andother parameters to prevent cracking except at the locations of thejoint structures.

As previously indicated, the joint structures remain very straight asthey are pushed into the concrete mass because they are highly resistantto transverse deflections or snaking because of the presence of the cap28 and cooperative structural relationship thereof with the channel 14.Not only does the cap 28 in structural association with the channel 14constrain the joint structure against flexing,'as explained, but itestablishes rather positively the depth to which the joint structure canbe depressed because of the relatively large surface area of the cap inengagement with the underlying concrete. Moreover, the wide cap 28 tendsto enforce a substantially vertical orientation onto the web 16 of thejoint structure and, correspondingly, to enforce a substantiallyhorizontal orientation onto the flange 15. Such accuracy in thepositioning of the joint structure is advantageous because it providesan enhanced functional association with the associated sections of theconcrete mass, and it also improves the aesthetic appearance of thefinished concrete product in that the upper surface of the flange 15 isessentially coplanar with the exposed upper surface of the concretemass. Insertion of the joint structure is facilitated by the pointedlower end 27 of the web, and the shoulder 26 tends to prevent spreadingof the web components 17 and 18 during insertion.

Once the joint structure (i.e., all of the joint structures in any givenarea of concrete) is inserted into the concrete mass, the concrete isprocessed and finished in a conventional manner which usually entailstamping the concrete to compact the same and bring moisture to thesurface of the concrete which is useful in subsequent finishingoperations. Tamping of the concrete can be effected in any conventionalmanner which, in many instances, is effected by a workman impacting ahand-heldtamping implement against the surface of the concrete. Next,the surface is smoothed with a large, flat tool that is referred to as abull float" and constitutes a large magnesium trowel-type implement thatmay be relatively heavy and spans a substantial area. The bull float ismoved freely over the cap 28 so that after this operation is completed,the upper surface of the concrete mass is essentially at the elevationof the upper surface of the cap 28, as shown in FIG. 4;

The tamping, and bull-floating procedures result in the concrete massbeing compacted tightly about the channel 14 and particularly againstthe web 16 thereof so as to underlie the flange 15 with substantially novoids or unsupported surface areas thereof. The mass also compactsfirmly against the arcuate spring fasteners 30 and 31 of the cap 28 soas to pre-cove the concrete mass along the transverse edges of theflange 15.

Following the bull-float processing of the concrete mass, the cap 28 isremoved from the channel 14, whereupon the assemblage has theconfiguration shown in FIG. 5. The cap 28 may be treated as a disposableitem and simply discarded, or it may be coiled or otherwise preservedfor reuse. Upon the removal of the cap 28, a slight depression will bepresent in the concrete corresponding to the thickness and extent of thecap 28, and such depressions are indicated in FIG. 4 by the numerals 34Aand 34B. Such surfaces have a relatively sharp outer transverse edge,and along the inner transverse edges thereof they curve downwardlytoward the under surface of the flange 15 in accordance with the arcuateconfiguration enforced on the concrete by the spring fasteners 30 and 31of the removable cap. The slight voids along the lower outer corners ofthe flange 15 created by the inner edges of the fasteners 30 and 31 (seeFIG. 4) tend to fill because of the fluidity of the concrete, as isindicated in FIG. 5. The workman then finishes the coating along thetransverse edges of the flange 15 either by use of a walking edger or ahand edger, either of which is in the nature of a trowel with an arcuateedge having the desired curvature and depth to be enforced on theconcrete along the coving. The edgers are sufficiently wide to extendoutwardly beyond the terminae of the depressions 34A and 34B so as tosmooth the same.

After the edging has been completed which may or may not be accompaniedby any necessary hand troweling to further smooth and finish theconcrete surface, the surface is given a final texture which maycomprise running brooms thereover to roughen the surface slightly andthereby provide an antislippage texture, or it may have a specialheat-reflective or resistive coating applied thereto such as FrontierKooldeck. In any case, after all of the finishing procedures have beencompleted, the protective strip 32 is removed quickly and easily andthereby leaves an unblemished upper surface, and the assemblage has theconfiguration shown in FIG. 6 in which the upper surface of the concretemass and surface of the flange 15 are substantially coplanar, and theconcrete surfaces merge with the flange along the coves 35A and 35B.

During all of the concrete-processing procedures, the upper surface ofthe flange 15 is protected at all times by the strip 32 and during theinitial processing steps by the cap 28. Therefore, the upper surface ofthe flange 15 is substantially unblemished when the concrete mass hascured and is ready for use. The flange 15 is thick relative to the web16 and anchors l9 and 20, and referenced to the upper wall member ofmany prior art water stop structures. Nevertheless, the total quantityof material used in the channel 14 does not exceed the total mass ofmaterial used in such prior structures. Not only is the flange lstructurally strong because of the mass of material therein but it iscompletely supported along the entire undersurface thereof by theunderlying mass of concrete, as is shown in each of FIGS. 4 through 7.Thus, the flange 15 is not readily deformed or perforated upon impactfrom sharp objects such as pebbles, narrow shoe heels, etc.

The anchors 19 and 20 are completely encapsulated or surrounded by theconcrete mass, and the vertical orientation of the anchor flanges 22 andprevents any tendency of the concrete to draw free from the anchor webs21 and 24 upon movement of the concrete mass, and especially theadjacent sections 11A and 11B thereof bounded by the common jointstructure. Such configurations of the flanges 22 and 25 together withthe rather long or tortuous path required for water to penetrate theconcrete mass along the joint structure makes the same an effectivewater stop inhibiting downward migration of water from the upper surfaceof the concrete to the earthen mass underlying the same. This isparticularly significant in soil that is adapted to swell when wet, andalso in areas sufficiently cold to cause the ground to freeze, each ofwhich conditions result in ground movement or heaving that tends toenforce relative displacements onto the concrete sections 11A and 118.

The joint structure when embedded into a concrete mass tends to localizecracks that develop in such mass by creating lines of weakness orintentional faults therein. This result is evident when it is understoodthat concrete is relatively weak in tension (although it has substantialcompressive strength), so that reducing the effective area of concreteto resist a tensile force applied thereto as by inserting a divider inthe form of the joint structure into the concrete mass, tends to causeany fissure in the concrete to occur along such restricted area: namely,that area underlying the joint structure 12. Any such crack that doesdevelop, remains concealed from view because of the presence of thejoint structure and does not, therefore, become aesthetically unsightly,and it also remains isolated from moisture because of the barrier orwater-stop function performed by the joint structure as a consequence ofits intermediacy between such crack and the exposed upper surface of theconcrete mass.

As previously indicated, any crack in the concrete mass tends to occurintermediate the sections 11A and 11B bounded in common by the stopstructure. Often, a crack develops as part of the curing procedurebecause the concrete necessarily shrinks or contracts somewhat as itlooses the heat developed during the curing process and therefor cools.Any such shrinkage might result in the somewhat exaggeratedconfiguration of the assemblage shown in FIG. 7 in which the webcomponents 17 and 18 have been displaced transversely relative to eachother, thereby leaving a void intermediate the same. The web components17 and 18 move in mechanically enforced displacement with therespectively associated concrete sections 11A and 118 because of theiranchorage thereto via the anchors l9 and 20, but the sections mayseparate below such anchors, as indicated by the cleavage or open area36 in FIG. 7. A similar type of relative displacement might occur uponother thermally-induced contraction of the concrete sections, and shouldthey tend to expand because of being heated and thereby move toward eachother, the void between the web components 17 and I8 simply tends toclose and the size of the cleavage or open area 36 reduces. The samegeneral accommodation of relative displacement occurs if the supportingsoil tend to heave, but whatever action occurs, it remains essentiallyconcealed from view and protected from water and other environmentalconditions.

It will be appreciated that whereas the snap-type interconnection of thetongue 26' and groove 26 provides a sufficient frictional interlock tomaintain the webs 17 and 18 closed during insertion of the jointstructure into wet concrete, it is of no significance in resisting theinexorable forces of contraction of the concrete mass. The absence ofvoids in the joint structure 12 materially reduces the buoyancy thereof,thereby making the joint structure essentially nonfloatable in wetconcrete. As a result, workmen are not required to repetitively push thejoint structure downwardly into the wet concrete to return the jointstructure to its proper position after it has risen or floated upwardlyclue to its buoyance, as in certain conventional arrangements.

As previously indicated, the channel 14 and cap 28 may be sold asseparate components, or may be sold in assembled form, as illustrated inFIG. 4. Accordingly,

the same cap 28 might be usuable a number of times with differentchannels 14. By way of giving a specific dimensional example forillustrative purposes, the flange 15 of the channel 14 may beapproximately onehalf inch in transverse dimension and have a verticalthickness approximating 3/32 of an inch. The transverse width of theanchors l9 and 20 from flange 22 to 25 thereof may be approximatelyone-half inch, and the overall vertical dimension of the channel fromthe upper surface of the flange 15 to the point 27 may be approximately1 /16 inches. The thickness of each web component 17 and 18 and of theanchor webs 21, 24 and anchor flanges 22, 25 may all be approximately0.030 of an inch. The cap 28 may have a transverse dimension ofapproximately 1% inches across the topwall 29, and a topwall thicknesssomewhat less than that of the flange 15, approximately one-sixteenth ofan inch. The fasteners 30 and 31 may have approximately the samethickness, and a length sufficient to grip the lower outer corners ofthe flange with an arcuate curvature of a one-fourth inch radius. Assuggested, the exemplary dimensions may be varied considerably, but havebeen found effective in specific embodiments of the invention.

While in the foregoing specification an embodiment of the invention hasbeen set forth in considerable detail for purposes of making a completedisclosure thereof, it will be apparent to those skilled in the art thatnumerous changes may be made in such details without departing from thespirit and principles of the invention.

What is claimed is:

1. A joint structure adapted to be embedded in concrete materials andthe like to accommodate relative displacements of sections thereofbounded in common by such joint, comprising: a longitudinally extendinggenerally T-shaped channel having a transverse flange defining a topwalladapted to be disposed in generally planar relation with the surfaces ofsuch sections and having also a web extending downwardly from saidflange, said web being divided intermediate the transverse edges thereofinto web components disposed in side-by-side juxtaposition anddisplaceable transversely relative to each other, means effective tosecure each of said web components to the associated section formovement therewith; a cap removably secured to said channel in generallyoverlying relation with said flange; and a strip of protective materialintermediate said flange and cap to protect the surface of the latter.

2. The joint structure of claim 1 in which said means comprises a pairof anchors respectively secured to said web components and projectingtransversely therefrom a spaced distance below said flange.

3. The joint structure of claim 2 in which said anchors are disposed insubstantial alignment and together have a generally l-shapedconfiguration.

4. The joint structure of claim 1 in which one of said web components islonger than the other and is provided with a transversely offsetshoulder underlying the end of such other web component to protect thesame during insertion of said joint structure into a mass of uncuredconcrete.

5. The joint structure of claim 4 in which said longer web component hasa progressively decreasing transverse dimension extending downwardlyfrom said offset shoulder to facilitate insertion of said jointstructure into a mass of uncured concrete.

6. The joint structure of claim 1 in which said web components andflange are integral, said web components being angularly displaceablealong the juncture thereof with said flange to provide the aforesaidrelative transverse displaceability thereof.

7. The joint structure of claim 6 in which one of said web components islonger than the other and is provided with a transversely offsetshoulder underlying the end of such other web component to protect thesame during insertion of said joint structure into a mass of uncuredconcrete.

8. The joint structure of claim 7 in which said means comprises a pairof anchors respectively secured to said web components and projectingtransversely therefrom a spaced distance below said flange.

9. The joint structure of claim 1 in which said cap is equippedtherealong with resilient fasteners releasably engageable with saidflange to removably secure said cap to said channel. 7

10. The joint structure of claim 9 .in which said cap is provided with agenerally planar topwall adapted to overlie said flange, said resilientfasteners depending from said topwall in transversely spaced relationand being substantially continuous elements cooperative with said flangegenerally along the length thereof.

11. The joint structure of claim 10 in which each of said resilientfasteners has an arcuate configuration effective to pre-cove along saidflange a mass of concrete into which said joint structure is embedded.

12. The joint structure of claim 10 in which the topwall of said cap issubstantially wider in transverse dimension than said flange so as tooverhang the same.

13. The joint structure of claim 1 in which said strip of materialcomprises a low-tack, pressure-sensitive tape releasably secured to saidflange along the upper surface thereof.

14. The joint structure of claim 13 in which said cap is equippedtherealong with resilient fasteners releasably engageable with saidflange to removably secure said cap to said channel.

15. The joint structure of claim 1 and further including means havingcooperative elements respectively provided by said web components tomaintain the same in generally contiguous juxtaposition during insertionof said joint structure into a mass of uncured concrete.

16. The joint structure of claim 15 in which said cooperative elementscomprise a tongue provided by one web component and a groove provided bythe other for receiving said tongue therein.

17. The joint structure of claim 16 in which one of said web componentsis longer than the other and is provided with a transversely offsetshoulder underlying the end of such other web component to protect thesame during insertion of said joint structure into a mass of uncuredconcrete, said groove being provided in said shoulder and said tonguebeing provided by the shorter of said web components.

18. In a joint structure adapted to be embedded in concrete materialsand the like to accommodate relative displacements of sections thereofbounded in common by such joint, a longitudinally extending generallyT-shaped channel having a transverse flange defining a topwall adaptedto be disposed in generally planar relation with the surfaces of suchsections and having also a web extending downwardly from said flange,said web being divided intermediate the transverse edges thereof intoweb components in generally side-by-side juxtaposition and displaceabletransversely relative to each other, each of said web components beingequipped with a transversely projecting anchor effective to secure thesame to the associated section of concrete material for movementtherewith, and one of said web components being longer than the otherand provided with a transversely offset shoulder underlying the end ofsuch other web component to protect the same during insertion of saidjoint structure into a mass of uncured concrete.

19. The channel of claim 18 in which said web components and flange areintegral, said web components being angularly displaceable along thejuncture thereof with said flange to provide the aforesaid relativetransverse displaceability thereof, and said longer web component has aprogressively decreasing transverse dimension extending downwardly fromsaid offset shoulder to facilitate insertion of said joint structureinto a mass of uncured concrete.

20. The channel of claim 19 in which said anchors are disposed insubstantial alignment and together have a generally l-shapedconfiguration.

21. The channel of claim 20 in which the channel is an elongatedcontinuous member integral throughout, said web being located adjacentthe center of said flange and having a substantially normal orientationwith respect thereto.

22. The channel of claim 19 and further including means havingcooperative elements comprising a groove disposed along said shoulderand a tongue provided by the shorter of said web components receivablewithin said groove to maintain said web components in generallycontiguous juxtaposition during insertion of said joint structure into amass of uncured concrete.

23. In a joint structure adapted to be embedded in concrete materialsand the like to accommodate relative displacements of sections thereofbounded in com mon by such joint, a cap adapted to be removably securedto the flange of a generally T-shaped channel to stiffen the latter andprotect the flange thereof, said cap having a relatively wide and thintopwall substantially wider than such flange and adapted to overlie thesame, said cap further having transversely spaced spring fastenersextending downwardly from said topwall and being formed integrallytherewith, and said fasteners each having an arcuate configuration toenforce a cove configuration onto any mass of concrete into which saidfasteners are inserted.

24. The cap of claim 23 in which said topwall and fasteners aresufficiently resilient to enable an elongated length of said cap to becoiled into a helical roll.

1. A joint structure adapted to be embedded in concrete materials andthe like to accommodate relative displacements of sections thereofbounded in common by such joint, comprising: a longitudinally extendinggenerally T-shaped channel having a transverse flange defining a topwalladapted to be disposed in generally planar relation with the surfaces ofsuch sections and having also a web extending downwardly from saidflange, said web being divided intermediate the transverse edges thereofinto web components disposed in side-by-side juxtaposition anddisplaceable transversely relative to each other, means effective tosecure each of said web components to the associated section formovement therewith; a cap removably secured to said channel in generallyoverlying relation with said flange; and a strip of protective materialintermediate said flange and cap to protect the surface of the latter.2. The joint structure of claim 1 in which said means comprises a pairof anchors respectively secured to said web components and projectingtransversely therefrom a spaced distance below saId flange.
 3. The jointstructure of claim 2 in which said anchors are disposed in substantialalignment and together have a generally I-shaped configuration.
 4. Thejoint structure of claim 1 in which one of said web components is longerthan the other and is provided with a transversely offset shoulderunderlying the end of such other web component to protect the sameduring insertion of said joint structure into a mass of uncuredconcrete.
 5. The joint structure of claim 4 in which said longer webcomponent has a progressively decreasing transverse dimension extendingdownwardly from said offset shoulder to facilitate insertion of saidjoint structure into a mass of uncured concrete.
 6. The joint structureof claim 1 in which said web components and flange are integral, saidweb components being angularly displaceable along the juncture thereofwith said flange to provide the aforesaid relative transversedisplaceability thereof.
 7. The joint structure of claim 6 in which oneof said web components is longer than the other and is provided with atransversely offset shoulder underlying the end of such other webcomponent to protect the same during insertion of said joint structureinto a mass of uncured concrete.
 8. The joint structure of claim 7 inwhich said means comprises a pair of anchors respectively secured tosaid web components and projecting transversely therefrom a spaceddistance below said flange.
 9. The joint structure of claim 1 in whichsaid cap is equipped therealong with resilient fasteners releasablyengageable with said flange to removably secure said cap to saidchannel.
 10. The joint structure of claim 9 in which said cap isprovided with a generally planar topwall adapted to overlie said flange,said resilient fasteners depending from said topwall in transverselyspaced relation and being substantially continuous elements cooperativewith said flange generally along the length thereof.
 11. The jointstructure of claim 10 in which each of said resilient fasteners has anarcuate configuration effective to pre-cove along said flange a mass ofconcrete into which said joint structure is embedded.
 12. The jointstructure of claim 10 in which the topwall of said cap is substantiallywider in transverse dimension than said flange so as to overhang thesame.
 13. The joint structure of claim 1 in which said strip of materialcomprises a low-tack, pressure-sensitive tape releasably secured to saidflange along the upper surface thereof.
 14. The joint structure of claim13 in which said cap is equipped therealong with resilient fastenersreleasably engageable with said flange to removably secure said cap tosaid channel.
 15. The joint structure of claim 1 and further includingmeans having cooperative elements respectively provided by said webcomponents to maintain the same in generally contiguous juxtapositionduring insertion of said joint structure into a mass of uncuredconcrete.
 16. The joint structure of claim 15 in which said cooperativeelements comprise a tongue provided by one web component and a grooveprovided by the other for receiving said tongue therein.
 17. The jointstructure of claim 16 in which one of said web components is longer thanthe other and is provided with a transversely offset shoulder underlyingthe end of such other web component to protect the same during insertionof said joint structure into a mass of uncured concrete, said groovebeing provided in said shoulder and said tongue being provided by theshorter of said web components.
 18. In a joint structure adapted to beembedded in concrete materials and the like to accommodate relativedisplacements of sections thereof bounded in common by such joint, alongitudinally extending generally T-shaped channel having a transverseflange defining a topwall adapted to be disposed in generally planarrelation with the surfaces of such sections and having also a webextending downwardly from said flange, said web being dividedIntermediate the transverse edges thereof into web components ingenerally side-by-side juxtaposition and displaceable transverselyrelative to each other, each of said web components being equipped witha transversely projecting anchor effective to secure the same to theassociated section of concrete material for movement therewith, and oneof said web components being longer than the other and provided with atransversely offset shoulder underlying the end of such other webcomponent to protect the same during insertion of said joint structureinto a mass of uncured concrete.
 19. The channel of claim 18 in whichsaid web components and flange are integral, said web components beingangularly displaceable along the juncture thereof with said flange toprovide the aforesaid relative transverse displaceability thereof, andsaid longer web component has a progressively decreasing transversedimension extending downwardly from said offset shoulder to facilitateinsertion of said joint structure into a mass of uncured concrete. 20.The channel of claim 19 in which said anchors are disposed insubstantial alignment and together have a generally I-shapedconfiguration.
 21. The channel of claim 20 in which the channel is anelongated continuous member integral throughout, said web being locatedadjacent the center of said flange and having a substantially normalorientation with respect thereto.
 22. The channel of claim 19 andfurther including means having cooperative elements comprising a groovedisposed along said shoulder and a tongue provided by the shorter ofsaid web components receivable within said groove to maintain said webcomponents in generally contiguous juxtaposition during insertion ofsaid joint structure into a mass of uncured concrete.
 23. In a jointstructure adapted to be embedded in concrete materials and the like toaccommodate relative displacements of sections thereof bounded in commonby such joint, a cap adapted to be removably secured to the flange of agenerally T-shaped channel to stiffen the latter and protect the flangethereof, said cap having a relatively wide and thin topwallsubstantially wider than such flange and adapted to overlie the same,said cap further having transversely spaced spring fasteners extendingdownwardly from said topwall and being formed integrally therewith, andsaid fasteners each having an arcuate configuration to enforce a coveconfiguration onto any mass of concrete into which said fasteners areinserted.
 24. The cap of claim 23 in which said topwall and fastenersare sufficiently resilient to enable an elongated length of said cap tobe coiled into a helical roll.